Our Universe Born From Collision With Another Universe?

Though
many physicists believe it’s possible that our universe is one of many in a
multiverse, they struggle to find concrete evidence to back up that
hypothesis. But now, we may find that
evidence.

That
is if we look for the wreckage left behind by a collision of cosmic
proportions. Over at Quanta, Jennifer Oullette explores one experiment that
could provide evidence for the multiverse. It assumes that our universe was
born during a collision with another universe — and that this dramatic event
may have left a cosmic imprint behind that we can measure.

Like
many of her colleagues, Hiranya Peiris, a cosmologist at University College
London, once largely dismissed the notion that our universe might be only one
of many in a vast multiverse. It was scientifically intriguing, she thought,
but also fundamentally untestable. She preferred to focus her research on more
concrete questions, like how galaxies evolve.

Then
one summer at the Aspen Center for Physics, Peiris found herself chatting with
the Perimeter Institute’s Matt Johnson, who mentioned his interest in
developing tools to study the idea. He suggested that they collaborate.At
first, Peiris was skeptical. “I think as an observer that any theory, however
interesting and elegant, is seriously lacking if it doesn’t have testable
consequences,” she said. But Johnson convinced her that there might be a way to
test the concept.

If
the universe that we inhabit had long ago collided with another universe, the
crash would have left an imprint on the cosmic microwave background (CMB), the
faint afterglow from the Big Bang. And if physicists could detect such a
signature, it would provide a window into the multiverse. Erick Weinberg, a
physicist at Columbia University, explains this multiverse by comparing it to a
boiling cauldron, with the bubbles representing individual universes — isolated
pockets of space-time.

As
the pot boils, the bubbles expand and sometimes collide. A similar process may
have occurred in the first moments of the cosmos.In the years since their
initial meeting, Peiris and Johnson have studied how a collision with another
universe in the earliest moments of time would have sent something similar to a
shock wave across our universe.

They
think they may be able to find evidence of such a collision in data from the
Planck space telescope, which maps the CMB. The project might not work, Peiris
concedes. It requires not only that we live in a multiverse but also that our
universe collided with another in our primal cosmic history. But if physicists
succeed, they will have the first improbable evidence of a cosmos beyond our
own.